1. Field of the Invention
The present invention relates to a method for manufacturing a golf club head.
2. Description of the Related Art
As a conventional technique, Japanese Patent Registered Publication No. 3059397 discloses a method for manufacturing a golf club head comprising the steps of forming a golf club head body from a forgeable metallic material of small specific gravity; providing a composite material member to a placing position locating inside the head body, the composite material member having large specific gravity compared to the head body and high melting point compared to the forging temperature of the forgeable material of the head body; and forming the head body by forging so as to confine the composite material member in the head body.
Moreover, Japanese Patent Registered Publication No. 3140991 discloses a method for manufacturing a golf club head joining a disparate metal member to a head body. This method comprises the steps of forming at least one opening or one concave portion on a head body member prior to shaping the head body; placing the disparate metal members in the opening(s) or concave portion; then joining the head body member and the disparate metal members together while forming the head body in a desired shape.
In the former method of the above-mentioned two conventional methods, a technique such as combining the head body with relatively small specific gravity and the composite material member of relatively large specific gravity is only available for lowering the C.G. of the head or enlarging the depth of the head (a distance between the center of the gravity of the head and a face) by placing the composite material member adjacent to the sole of the head, and thus the degree of freedom of designing the head would be limited. Moreover, as described above, the composite material member having larger specific gravity than that of the head body and higher melting point than the forging temperature of the head body is provided on the placing position inside the head body according to the first introduced method. This results in the fact such that the head body would crack up when the temperature of the inside of the head body does not reach the forging temperature, while it would be overheated when the temperature of the inside of the head body reaches the forging temperature. In order to prevent the head body from cracking, the composite material member needs to be placed on a portion of the head body where amount of the deformation due to forging is less. Accordingly, the degree of freedom of designing the head is further limited.
On the other hand, according to the latter conventional method, the opening(s) or concave portion is formed on the head body member prior to shaping the head body. Accordingly, the whole metallic material for forming the head body member is not utilizable, and thus there is a limitation in the reduction of the manufacturing cost.
Moreover, in a case manufacturing a wood type metal head by integrating a plurality of metallic shells while using the latter conventional method, a thickness of each metallic shell is generally arranged about 3.0 mm from a standpoint of effectiveness or the like. In this thickness, however, the head body including the disparate metal members would crack up when the temperature of the inside of the head body does not reach the forging temperature, while it would be overheated when the temperature of the inside of the head body reaches the forging temperature. By suitably designing the placing position of the disparate metal member, the head can be prevented from cracking, but the degree of freedom of designing the head is resultantly limited.